I’ll Show You My Holiday Card If You Show Me Yours.

Earlier this week, my husband and I returned home from our holiday travels after being away from our apartment for the past 9 days. We walked into our chilly apartment, greeted our whining cats with a quick pet and a kiss hello, put down our bags, and walked into the kitchen.

Earlier this week, my husband and I returned home from our holiday travels after being away from our apartment for the past 9 days. We walked into our chilly apartment, greeted our whining cats with a quick pet and a kiss hello, put down our bags, and walked into the kitchen. Our cat sitter always checks our mail while we're gone, and she typically leaves the handful of catalogs, coupon fliers, and newsletters that we receive in a small pile on our counter.

But this time, when we walked in, it was no small handful of mail. We had come back to a veritable slew of cards, all with Christmas trees on their stamps and familiar last names on the return address labels.

Now, my husband and I have received holiday cards before. A few years ago, one of my friends from high school sent me a Christmas card along with her husband -- although mostly it was because that year, their Christmas cards were doubling as a "Surprise, there will be a mini version of us arriving in May!" announcement. We usually get a card from my parents, who we don't spend Christmas with (I'm Jewish), and any of my in-laws that we don't happen to see while we're visiting my husband's hometown. But not this. Not this "veritable slew." This, quite frankly, was unprecedented.

However, I should really be honest here. Although it was unprecedented, it wasn't exactly unexpected. There was one big thing that we did differently this year, after all.

We sent out cards of our own.

As a social psychologist, I can promise you one thing -- if you like receiving holiday cards, sending out a card of your own is the fastest way to guarantee that by December 25th, your fridge will be covered in images of Yuletide joy. In fact, back in 1976, sociologists Phillip Kunz and Michael Woolcott used Christmas cards in an experiment to see just how many people would reciprocate the receipt of a holiday card by mailing their own Christmas cards back...to perfect strangers.

Yes, you read that right. Perfect strangers. Kunz and Woolcott picked the names of 578 perfect strangers from the Chicago city directory and mailed them Christmas cards. Not everyone got the same exact card, mind you. Some people got expensive, high-quality cards decorated with poetry inscriptions and beautiful wintery scenes, while others got plain, white cards with "Merry Christmas" handwritten in red Sharpie marker across the front. Some people received their cards from "Dr. and Mrs. Kunz," while others simply received a card signed from "Phil and Joyce." But in every case, two facts remained -- people received a card with a clearly marked return address, and that return address had the names of two people that they had never met before in their entire lives.

What would you do if you received a card from a perfect stranger? In this case, six of the strangers wrote back and directly asked Dr. Kunz for more information on how exactly they were acquainted. Another Chicago family with the last name Kunz actually reported that they had to call the police and complain about the number of people who had contacted them throughout the month of December, desperately seeking more information about who on earth Phil and Joyce were and how they could possibly know them. The experiment actually generated enough local buzz that it eventually ended when a local radio station outed the ploy, thus contaminating the potential authenticity of any future responses.

But before that happened, 117 of the recipients -- a full 20% of the original sample -- had sent their own responses back to Kunz and Woolcott. These responses ranged from a simple mailing back of their own generic holiday cards, to pictures of their children and pets, to several-page-long letters detailing what had been going on in their lives over the past few years. Despite the fact that they had never actually met Phillip Kunz before in their lives, 20% of the recipients felt the need to respond to his Christmas card by sending their own cards back.

This study is often used as an illustrative example of the norm of reciprocity -- when people do something nice for you, you will likely feel extremely uncomfortable not returning the favor. If someone buys you a soda, you'll probably be more likely to buy some of the raffle tickets that he later tries to sell you. The Hare Krishna are intimately acquainted with this norm -- it's why they will hand you a flower in the airport before asking for a monetary contribution. So, when you receive a holiday card -- even if you don't quite know how you are acquainted with the card's sender -- you will likely feel very pressured to reciprocate with a card of your own.

Which brings me back to the pile that greeted me and my husband when we returned home from our holiday travels. Sure, some of those friends and family members may have intended to send us cards no matter what. But as much as I love our loved ones and have faith in how much they truly do care for us...I'm also absolutely sure that some of them only sent us cards because they received their cards from us first.

In the end, though, I'm OK with it. After all, it definitely came in handy having all of those holiday cards that we printed out when we received a few last-minute cards from people not on our original list -- and we knew, of course, that we really needed to quickly send them something nice back.

Note: Interestingly, this study is often used as an example of the norm of reciprocity, but the authors never use this term -- or even claim to be testing it -- in the original paper. The study was actually conducted to examine which factors would change the rates of response -- they found that people were more likely to respond back to higher-quality cards (30% for the higher-quality cards vs. 15% for the lower-quality cards) and when the senders were higher-status (26% of the recipients returned cards to Dr. and Mrs. Kunz, whereas only 15% returned cards to Phil and Joyce). However, in order to even do this study, Kunz and Woolcott had to (correctly) have the underlying assumption that people would feel compelled to return Christmas cards to perfect strangers at all. So, if you really want to guarantee a good return on your holiday card investment, you should probably go for the more expensive cards. And make your names sound fancy on your return address labels.

Regan, D. T. (1971). Effects of a favor and liking on compliance. Journal of Experimental Social Psychology, 7,627-639.

All photographs were taken by the author.

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

ABOUT THE AUTHOR(S)

Melanie Tannenbaum

Melanie Tannenbaum is a freelance writer and science communications consultant currently living in the Bay Area. She received her Ph.D. in social psychology from the University of Illinois at Urbana-Champaign in 2015, where her research focused on the science of persuasion and motivation regarding political, environmental, and health-related behavior. For more info, see her personal website.

Scientific American is part of Springer Nature, which owns or has commercial relations with thousands of scientific publications (many of them can be found at www.springernature.com/us). Scientific American maintains a strict policy of editorial independence in reporting developments in science to our readers.